Argus video-based monitoring at Ostend, Belgium Analysis of coastal changes in 2013

Overview of this presentation Ostend Argus station Shoreline Mapping Coastal dynamics at Ostend Web-based access to Argus data Conclusions Future

Objectives Context of Blast project: harmonization of datasets Deployment of an Argus station Analysis of coastal dynamics at Ostend Long-term changes  IBM Impact of storm events  ASM Web-services web-based access to (raw) data and products Calculation and visualization

Ostend project site

The Argus Technique Data Connection Cameras Image Sampler Field Computer Archive computer Field System Local System Argus video system

Argus station – location

Argus station – resolution maps

Argus data collection strategies

GCP Horizon Image Quantification

Web-services web-based access to (raw) data and products, i.e snap, timex, merges Merged plan view images

Mapping intertidal beach bathymetry from a set of shorelines, derived from time-averaged video observations throughout a tidal cycle. Mapping intertidal beach bathymetry

IBM (Intertidal Beach Mapper)

AutoShoreline Mapper

Autoshoreline application at Ostend

Analysis of coastal dynamics at Ostend Context: Availability of bathymetric survey in June 2012 Storms in winter 2013 Objectives Assessment of long-term changes, based on bathymetries retrieved from manually detected waterlines Assessment of the impact of storm events, based on bathymetries retrieved from automatically detected waterlines

Wave diffraction and attenuation by the harbour breakwaters Need to take into account this process when applying the elevation model Accounting for site specificities at Ostend

Presence of wet sand in the upper part of the intertidal beach during the falling tide Intertidal beach mapping at rising tide only Accounting for site specificities at Ostend

Methodology 1. Calibration of elevation model against surveyed data 2. Manual mapping for acquisition of monthly bathymetric data (September 2012 – October 2013) 3. Automated mapping for acquisition of data: calibration 1.Individual runs 2.Combined runs 4.Hydrodynamic conditions 5.Seasonal evolution 6.Storm response 7.Influence of coastal structures

Calibration of the elevation model for Ostend site  sensibility analysis on the beach slope mb and the swash parameter k osc Best settings for Ostend using IBM: mb = 0 and k osc = 0  no wave contribution 15 augustus 2013 Calibration of elevation model

Loess interpolation MonthComputed bathymetries September /06/2012 October /10/2012 November /11/2012 December /12/2012 January /01/2013 February /02/2013 March /03/2013 April /04/2013 May /05/2013 June /06/2013 July /07/2013 August /08/2013 October /10/2013 Acquisition of monthly bathymetric data

Calibration period: 30/01/2013 to 15/02/2013 Characteristics Mean Hrms = 0.66 m Energetic event:  02/02/2013 to 07/02/2013 Spring and neap tide cycles Automated acquisition of data: calibration

RunParameter setting Reference case (ASM-RC)Default settings Specific images (ASM-SI) Rising tide images  ARE filtering function ASM_risingTide Lower storm threshold (ASM-LST)Storm threshold = 1.5 m Larger smoothing scales (ASM-LSS) Smoothing scales: L x = [25; 50], L y = [50;150] Partial wave contribution (ASM-PWC) For Hrms 1 m  mb = 0.01 and k osc = 1, using ARE function ASM_wavesContribution Shifts (ASM-S)Seaward & landward shifts set to 100 m Run twice (ASM-RT)1 day, 2 successive runs Mb and kosc rectified (ASM-MKR)mb = and k osc = 1.3 Automated acquisition of data: calibration

Runs with combined developements (ASM-CD) ASM-CD1ASM-CD2ASM-CD3 Images filteringRising tide images Storm threshold1.5 m Smoothing scales L x = [25 m; 50 m] L y = [50 m; 150 m] L x = [25 m; 50 m] L y = [50 m; 150 m] L x = [25 m; 50 m] L y = [50 m; 150 m] Wave contribution Partial: for Hrms > 1 m  mb = and k osc = 1, else mb = 0 and k osc = 0 Full: mb = 0.025; k osc = 1.3 Zero: mb = 0 and k osc = 0 Automated acquisition of data: calibration

Run15/02/2013 ASM-RC0.273 (16911) ASM-SI0.137 (18767) ASM-LST0.2 (17881) ASM-LSS0.188 (17190) ASM-PWC0.141 (16826) ASM-S0.149 (16179) ASM-RT0.201 (17358) ASM-MKR0.131 (16489) Rms difference IBM-ASM (m) and number of points processed in brackets Run15/02/2013 ASM-CD (16451) ASM-CD (17211) ASM-CD (17255) * ASM-CD1 = partial wave contribution; ASM-CD2 = full wave contribution; ASM-CD3 = no wave contribution Automated acquisition of data: calibration

Hydrodynamic data between September 2012 to November 2013: Offshore tidal level (m); Offshore significant wave height H rms (m); Waves peak period T peak (s); Longshore energy flux P long (J/m/s). 18/09/2012 to 20/10/2013 mean H rms = 0.46 m mean T peak = 5.58 s mean Th0 = 306ºN  WNW waves Two wave climates Hydrodynamic conditions

Winter wave climate mean H rms = 0.48 m Mean T peak = 5.81 s Mean Th0 = 305ºN  WNW 5 energetic events over 1.5 m Summer wave climate Mean H rms = 0.42 m Mean T peak = 5.01 s Mean Th0 = 313ºN  WNW No energetic event over 1.5 m Hydrodynamic data between September 2012 to November 2013: Offshore tidal level (m); Offshore significant wave height H rms (m); Waves peak period T peak (s); Longshore energy flux P long (J/m/s). Hydrodynamic conditions

Similar trends at 3 different alongshore positions Retreat of the beach during winter and accretion in summer Seasonal evolution Contour lines retrieved from IBM for 3 alongshore locations

Contour lines retrieved from IBM (blue), ASM-CD1 (light blue line), ASM-CD2(green) and ASM-CD3(red) for m (solid line), -650 m (dashed line) and -100 m (dashed/dotted line) alongshore locations Beach erosion during the storm Reconstruction and accretion of the beach with post-storm conditions Storm response

ASM-CD1 in agreement with IBM bathymetries Discrepancies for the May and June 2013 bathymetries Storm response Contour lines from IBM & ASM-CD1 for m, -650 m and -100 m alongshore locations

Web-based access to Argus data and products Provision of information to MDK | Afdeling Kust & general public Flexibility and reactivity ensured through the use of a website background information on Argus and the Ostend site; a means to browse the image archive in various ways; the ability to perform certain calculations and visualize the results, giving the end-user maximum flexibility. Website can be opened to the public; other parts will require a user name and password.

Conclusions Objectives and activities Successful deployment of an Argus video-based remote sensing station at the location of Ostend (Belgium) to monitor morphological changes of the beaches. Beach bathymetry mapping performed using IBM (manual) and ASM (automated). Bathymetries constructed based on monthly detected waterlines for more than a year and based on waterlines detected over consecutive days from February to June 2013 (5 months)

Conclusions Coastal dynamics Seasonal pattern observed as a function of the frequency and intensity of storms in summer and winter. Beach retreat estimated to be of about 30 m during the winter season, followed by a recovery during the summer season Similar rate estimated at three different alongshore locations Beach response to a storm event identified as erosion (beach retreat of about 20 m) followed by accretion in case of mild wave post-storm conditions

Conclusions Web-services Flexibility and reactivity ensured through the use of a website Background information on Argus and the Ostend site; Means to browse the image archive in various ways; Ability to perform certain calculations and visualize the results, giving the end-user maximum flexibility.

Future of Argus at Ostend The current station Continuity on data acquisition, maintenance Follow-up on processing, e.g. (automated) ASM long-term application with additional IBM mapping Web-access to Argus data and products, and dissemination of information Other activities (e.g. cBathy, beach user counting) A new station in Ostend Current status Use of hardware from existing station Combination of efforts by Kust and FHR for maintaining the existing station